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mocha has always been very popular as a tracking tool, but with the rising interest in stereo 3D conversion, its rotoscoping capabilities have become a favorite player in that pipeline and sales have soared. In this course, Steve Wright covers the basics of operating mocha, as well as advanced tracking and rotoscoping techniques. The course also covers the mocha/Nuke stereo 3D production pipeline in detail.
Selecting the right start frame for a shape is very important. You want to start on the most complex frame to minimize the need to insert new control points later. This also means you'll have different start frames for different parts of the body. Take a look at this hand here. If we scrub through the shot, you can see the outline of this hand is rather simple here, let's zoom in a little bit. As we scrub through the shot, the fingers open up, presenting a more complicated outline.
We will keep going, and out forms a fist, so the outline here would be simpler and to the end of the shot. Okay, so somewhere right around here where the fingers are spread out the white as would represent the most complicated outline and that would be where we would want to start rotoing the hand. Let's take another example. Let's take a look at the torso here. So I will scrub through the shot and ah! Look at here, right around here. look at all of the folds in the cloth here. So this frame might represent the most complicated outline because the outline of the torso might go like up here, up to there, over the shoulders and down the side and then they overlap here in the front, we don't care about.
So that would be the most complicated outline and we would scrub through the rest of the shot. See how much simpler this edge is here and continuing on through the shot. Okay, so we will call that the most complicated outline and that will be where we would start torso. Let's take one last case, this is the one we'll actually work on which is the head. Okay, we have a pretty simple outline here on the face, as we scrub forward, the head turns which happens all the time and now we have all of this complex curved surface here.
lips, nose, mouth, eye indent. So the most complicated frame for the head would be somewhere in this neighborhood. So I've already drawn a shape. So, we will turn that on and select the keyframes, there we are and we'll jump to this keyframe here. To keep things organized for you, the head.mocha file in the Project Media folder only have the head roto. Turn the Mattes off. So this would represent then our start frame for the head.
The reason that we want to start with the most complicated outline is we really like to avoid inserting new control points over the length of the shot. This introduces some problems. We'll see later what those problems are. We also always want to have the fewest possible control points on any spline, the reason is to avoid jitter, once you get jitter introduced it becomes very hard to fix. pushing in here a little bit. If the camera were closer, we might actually break this head into several separate shapes, one for the ear, the nose, forehead, the lips and the chin, so we might have four, five shapes.
But since the camera is this far away, we can get by with just this one shape. So I will select the shape again and I have a keyframe here on 43. So I am going to set the out points here to 43 and I will set the in point to frame 12. This will be the range I will be working with. I will pan the viewer with the X key and zoom in with the Z key and now we'll take a look at our new keyframe up here, right here on frame 12, you see how much simpler the outline is here.
So let's place the keyframe here and see how we might do that. Select that, select all the control points, Q key for a Translate tool, move it up here. Okay, now we'll reposition, zoom in a little closer. Sometimes it's very helpful to turn off the tangents right here, this button. That way, you can just move the control points without worrying about all those little tangent lines being in our face, and we get these scooched in here and bring that in there.
On this keyframe, the other side of the head has become more complicated, so we'll deal with that in a minute. But this is the thing I wanted to show you. After repositioning all of these control points, fine-tune that, however I've ignored the tangents, right? Now, the problem is, see how lumpy the curve is? Well, we can fix that very easily by selecting all those points, doing a right-mouse pop up point smooth and now all the tangents will be made parallel, I will turn the Tangents back on.
See how nice they are. All right, I can refine that a little bit, move the points in here, in there, and get a nice, smooth edge and once again select these points, right-mouse pop up and say Smooth and all the tangents will become smoothed up. Okay, so let's say we're happy with that. Now we need to take a look at this part of the problem where we've actually got increased complexity.
I will turn on my Spline and once again I am going to turn the Tangents off. I will switch to the Insert Control Point tool by typing I on the keyboard and now I get the insert cursor. So now I am going to sit here and insert a bunch of control points, trying not to move the old ones anymore than I have to. You notice there are some wrinkly anomalies, don't worry about that. We'll deal with that in just a moment. Okay. All right, let's say we're happy with that.
This is the problem you get when you insert control points because these control points have been inserted between old control points that already had their slopes set, see the tangents. So rather than coming in here and individually trying to adjust each and every one of these, again we're going to use that smoothing feature. So I am going to select all these points here. Maybe I want to get a couple of more by holding the Ctrl or Command key. Now that I have the effect control point sampled, I am going to pick any one control point, right-mouse pop up, Point > Smooth and then all the tangents now line up.
We'll deselect and take a look at our shot, move back out a little bit. Okay, so let's say we're happy with that. Actually, we're not, we have a few little issues that we need to deal with but I don't want to spend all day twiddling control points in front of you. That's not fun, so I am going to actually smooth these a little bit here and let's pretend this is good. Okay, all right! We've inserted new control points on frame 12. But that's caused problem back on the previous keyframe, let's go and see what happens.
I will select the spline, scrub the playhead back to my first keyframe, okay we were good before but now we have new kinks and wrinkles, look at this. See that? Here's a good one, oh, here's a bad one. The reason is, as before, we've inserted keyframes between points that already have their tension handles adjusted like this one here, okay? So what we need to do is relax all those tensions exactly like we did before.
So I will just select a whole bunch of points, use Command and Ctrl maybe to add one or two more that we want, maybe subtract one or two that we don't want, and then right-mouse pop up Point > Smooth and that will relax all the tensions on all the control handles getting rid of all of the kinks. Let me pull out here a little bit. Now, let's do a mid keyframe. I am going to select this guy here and scrub here to around frame 27. So we've got two extremes, one over here at 12, one over here at 47 and here's an in-between frame.
So I am going to pick up my Translate tool, move the spline over and by golly it's done a pretty darn good job at making an in-between frame for me. Let's deselect, scoot in, we'll refine some control points. Again, keeping the control point twiddling to a minimum, right? Actually that's not bad at all. Maybe we would like to smooth out some of this hair, Point > Smooth, okay, All right.
So let's say we like that. The point I want to make here is what we call temporal coherency, keeping control points associated with a body part over time. That's the temporal part. The coherent part is staying in the same place. I will give you an example. I will select the nose, I am going to turn off the tangents and I am going to select this control point for the nose, I will zoom out a little bit. If I come over here to this keyframe, you could see that control point is on the nose as it is here, and when we go to the keyframe on 12, it's sort of just melted into the side of the head.
So the important point is that control point wants to always stay associated with the nose. Let's take another case, there's the chin. Watch this control point, stay associated with the chin all the way through the entire timeline and that's temporal coherency. This is an extremely important part of good rotoscoping. If the control points slip and slide around the spline, they're going to introduce chatter. And again, once you've got chatter in, it is very hard to fix.
Okay, we'll deselect this, rehome the viewer and close by saying, even though you have carefully planned the shapes animation, sometimes after you get into it, you discover you've made a wrong choice. Don't be afraid to delete and start over when needed. The final result will be better and quicker rather than struggling to fix the bad start.
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